NeTS-NBD: Bridging the 10 GHz / 10 Gbit Gap: Whole-system approaches for scalable networked services

我们很快就会进入10 GHz处理器和10千兆位网络的时代，但还没有有效的方法来使用这种处理能力来为常规应用提供这种水平的吞吐量。这一差距存在于“服务堆栈”中，它包括网络系统(Web服务器、邮件服务器、缓存Web代理服务器、网格服务等)使用的应用程序级软件、操作系统和网络代码。理想情况下，这些系统的性能会随着更快的CPU而相应提高，但实际的改进可能会因为各种原因而显著降低，包括操作系统限制、磁盘性能改进较慢、CPU功能使用不佳等。这项工作从CPU的角度检查服务堆栈，以了解它与现代处理器功能之间的不匹配如何降低所提供的性能。最终目标是开发随处理器速度扩展的网格/网络应用程序，并使开发人员更容易提高性能。智力优势：首席调查员(PI)专注于三个领域：1.改进用于跨边界发现性能问题的工具，例如程序和操作系统之间的问题，以及操作系统和硬件的设备驱动程序之间的问题；2.使用这些工具重组操作系统中的网络代码，以优化常见情况；以及3.改进工具，以发现跨边界的性能问题，如程序和操作系统之间的问题，以及操作系统和硬件设备驱动程序之间的问题。开发一个可以自动定制操作系统以适应特定程序的系统，而不需要开发人员手动修改操作系统的源代码。调查的主要领域将是PIS所称的跨界问题，即两个没有明显缺陷的系统/层在一起使用时性能可能会很差。性能问题通常源于不同层中的使用假设不匹配。例如，使用“事件驱动”设计方法的Web服务器在“静态”内容(如常规文件和图像)上表现出了出色的性能和可伸缩性。然而，在这种情况下，它们的设计也需要操作系统存储大量关于程序的信息，并且当服务器处理诸如定制网页之类的“动态”内容时，在某些处理步骤中必须复制这些信息。随着服务器变得更加繁忙，这种交互会导致他们在动态内容上的性能下降。如果正在进行其他搜索，文件系统中的其他设计假设可能会导致所有类型的服务器在搜索文件时不必要地阻塞。这会导致CPU在磁盘访问期间未得到充分利用，这是一个问题，因为CPU速度的增长速度一直快于磁盘访问时间。因此，此类问题造成的相对性能损失将随着时间的推移而增加。除了开发具有更高性能并旨在更好地利用CPU的新网络服务堆栈之外，这项工作的另一个重点是检查这种优化的过程。更广泛的影响：私人投资机构将利用暑期实习来吸引传统上代表性不足的群体，同时也为了让私人投资机构在使用该系统时可以密切观察开发人员。实习的重点要么是优化一些开源系统，如MySQL数据库或Squid Web代理服务器，要么是扩展工具本身。通过使用具有不同专业水平的开发人员，PI可以衡量工具如何揭示最有希望进行进一步调查的领域。PI还可以将这些实验的反馈合并到使用这些工具的界面中，不仅可以增加互动性，还可以帮助非专家使用这些工具。

We will soon enter an era of 10 GHz processors and 10 Gigabit networks, but will have no effective means of using that processing power to deliver that level of throughput for regular applications. This gap lays in the "service stack," which includes the application-level software, the operating system, and the networking code used by networked systems (Web servers, mail servers, caching Web proxy servers, Grid services, etc). Ideally, the performance of these systems would improve correspondingly with faster CPUs, but actual improvements may be significantly lower for a variety of reasons, including operating system limitations, slower improvements in disk performance, poor use of the CPU's features, etc. This work examines the service stack from the CPU's perspective to understand how the mismatches between it and modern processor features reduce delivered performance. The ultimate goal is to develop Grid/networking applications that scale with processor speed, and to make it easier for developers to improve performance. Intellectual Merit: The principal investigators (PIs) focus on three areas:1. Improving the tools for finding performance problems across boundaries, such as those between programs and the operating system, and between the operating system and the device drivers for the hardware; 2. Using these tools to reorganize the networking code in the operating system to optimize common cases; and3. Developing a system that can automatically customize the operating system to be tailored for specific programs, without requiring the developer to manually modify the operating system's source code. The main area of investigation will be what the PIs term cross-boundary problems, where two systems/layers that have no obvious flaws can perform poorly when used together. The performance problems generally stem from a mismatch of usage assumptions in the different layers. For example, Web servers using the "event-driven" design approach have shown exceptional performance and scalability on "static" content, such as regular files, and images. However, under such conditions, their design also requires the operating system to store a large amount of information about the program, and this information must be duplicated during certain processing steps when the server handles "dynamic" content, such as customized Web pages. This interaction causes their performance on dynamic content to drop, as the server gets busier. Other design assumptions in filesystems can cause all types of servers to unnecessarily block when searching for files, if other searches are in progress. This results in the CPU being underutilized for the duration of a disk access, which is a problem since CPU speeds have been growing faster than disk access times. As a result, the relative performance loss from this kind of problem will grow over time. Beyond developing a new network service stack that has higher performance and is designed to better utilize the CPU, the other focus of this work is examining the process of this kind of optimization. Broader Impact: The PIs will use summer internships both to attract traditionally under-represented groups, but also to have developers the PIs can closely observe as they use the system. The focus of the internships will be either to optimize some open-source system, like the MySQL database or the Squid Web proxy server, or to expand the tools themselves. By using developers with various levels of expertise, the PIs can gauge how the tools can reveal the most promising areas for further investigation. The PIs can also incorporate the feedback from these experiments into the interface for using these tools, not only to increase interactivity, but also to help non-experts use them.